If you are going to develop for an embedded linux target you need a lot more then just Qt cross compiled. You can use something like Open Embedded, PTxdist or LTIB to build your root file system which would handle building Qt. Most of these tools allow you to select different toolchains.

As for the using the Mac - I can appreciate the desire to use the Mac since I am a Mac user myself but as you have seen that will prove difficult to manage. I suggest using VMware or Virtual Box and installing one of those "not so nice linux desktops" for embedded development.

If the root filesystem is already given, why would he need Open Embedded or anything similar? If the root filesystem is already given, along with the correct toolchain, compiling Qt should be sufficient.